Field of the Invention
The method of supporting an inertial member of a gyroscope by means of electric fields is well known in the art. Various systems have been devised, exploiting the inherent advantages offered by electric field suspension. One such system is described in U.S. Pat. No. 3,469,457, wherein the inertial member is shown supported by electric fields between three pairs of electrodes. Each pair of electrodes is energized by an electronic channel, supplying the electrodes with electric charge. In the quiescent state, when no external forces are being applied to the inertial member, the electric charges on the various electrodes are substantially equal. The magnitude of these charges in the absence of external forces is commonly referred to as the preload bias.
As an external force is applied to the inertial member, the charges on the electrodes are automatically altered so as to oppose the displacement of the inertial member from the center of the electrode cavity. This means that the charge on one electrode along the axis of the force must increase, in relation to the charge on the electrode at the opposite side of the inertial member. In the prior art systems, the maximum charge obtainable on any one electrode is equal to twice the preload bias charge. The maximum rebalance force is achieved, therefore, when the charge on one of the electrodes is twice the preload bias charge, while the charge on the other electrode is reduced to zero. Under such an arrangement, an inertial instrument with high acceleration response capability is required to maintain a correspondingly high preload bias. The preload bias forces between electrodes and the inertial member must at all times be high enough to assure the support of the inertial member under maximum anticipated shock and vibration loading.
The overall gain of prior art linear suspension system is proportional to the preload bias force. This interdependence of preload bias force and suspension gain is characteristic of the prior art suspension systems. It is clear, however, that under normal operating environment, the acceleration to which the inertial instrument is subjected is relatively low and that the inertial member is subjected to relatively large acceleration forces only on certain occasions and for brief intervals. Thus, the preload bias could be substantially reduced when operating under normal environment if means are provided to automatically increase the bias when the inertial instrument is subjected to external forces. Lower preload bias will result in reduction of errors due to drift, which is introduced by high bias forces because of imperfections in the sphericity and mass balance of the inertial member.